The characteristics of speed, torque (turning or twisting force), and power (rate or speed at which work is performed) for a typical internal combustion engine in a motor vehicle such as a motorcycle or a car usually do not match the requirements of the final propulsion component. For example, the range of output of the engine in a motorcycle does not match the range of requirements of the wheels in contact with the road surface. A clutch, disengageably connecting the engine to the transmission, provides the means to apply and remove engine torque to the transmission's input drive shaft.
A typical clutch assembly for a motorcycle includes a clutch lever located at or near the handlebar, and a clutch disengagement mechanism connected to the clutch lever by a clutch cable. The clutch is disengaged by activating the clutch lever which requires pulling of the clutch cable on its end. This simple standard approach has a number of disadvantages, including the cable becoming broken or extended over time, and the physical effort required to disengage the clutch lever. As a result, the clutch may not be fully disengaged unless the driver put in significant effort, which in itself may be distracting and lead to loss of control. The cable may also be trapped and rendered stuck against mechanical feature of the entire assembly.
GB2,233,408 refers to an electro-pneumatic gear-change system with emergency back up pressure source for a variable-speed gearbox, in which the gear selections are made pneumatically via actuating cylinders which are controlled by solenoid valves.
U.S. Pat. No. 5,033,598 discloses a combined mechanical and fluid pressure actuated slider clutch for a motorcycle including fluid power source supplying pressurized fluid for energizing pressure actuated controls wherein the fluid power source is pneumatic pressure.
U.S. Pat. No. 5,360,381 relate to a programmed automatic control for motorcycle and motor vehicle mechanical clutches activated by pneumatic source means wherein the power source is a motorcycle engine.
US patent application 20040055849 refers to a clutch, in particular for motor vehicle, with pneumatic control applicable to industrial vehicles equipped with a pressurized gas source. The application discloses a pneumatic actuator to control the disengaging of a clutch.
From US patent application 20020104731 is known a pneumatic powered clutch linkage entailing a conventional mechanical clutch to be powered or actuated through a powered fluid or pneumatic cylinder and thereby relieving the operator of the requirement of continuously and repeatedly actuating the clutch through a foot operated clutch pedal.
One approach, as seen in U.S. Pat. Nos. 6,102,183 and 6,227,342 both relating to motorcycle clutch systems, is to use hydraulic activation of the clutch disengagement mechanism. Hydraulic activation has the disadvantage of a fairly slow disengagement rate. A high disengagement rate is particularly crucial in certain cases, e.g. motorcycle racing.
There is a need to provide a way of activating the clutch disengagement mechanism such as to remove or minimize the disadvantages mentioned above.